Pennington School - the Holy Spirit, some water and a sponge?

This morning we went to Pennington School and did a talk in the assembly about Pentecost.  Before we started Sarah asked if anyone knew what in the Christian/church calendar Sunday was.  A few people put up their hands and the answer came out Pentecost.  I then told the story of Pentecost using a Bob Hartman version from his book Telling the Bible.  I followed this with a little explanation but mentioned several times the Holy Spirit - which Sarah then asked me about.  I then took a picture which was covered in blue paint and a sponge.  I explained that I couldn't clean the picture with the sponge - why?  Well I needed something else - water.  I put the sponge into a bucket of water and held it up - now it looked no different to before but I could then use it to clean the picture.  What was the difference it was the water inside it.  I explained that the Holy spirit is like that we don't look any different but it enables us to do the job God intended us to do which is tell other people about him.  Sarah then said that when we do that we Shine from the inside out which was the cue for the song.  I concluded by saying a prayer.